This invention relates to a method for evaluating a lithium manganese spinel material which is a cathodes material of a lithium rechargeable battery.
At the present time, a lithium transitional metal oxide (such as LiCoO.sub.2 or LiNiO.sub.2) has been developed and used as a cathode material for a lithium ion battery utilized in portable equipment, and a lithium manganese spinel, such as LiMn.sub.2 O.sub.4, has drawn attention as an advanced, low-cost, 4 V-grade cathode material and is currently under research and development.
The operating voltage and charge and discharge capacities of lithium batteries using this material is very sensitive mainly to the valency and distribution of Mn ion in the crystal structure. This means that properties of lithium ion batteries vary greatly depending upon conditions for the production of a powder for a cathode material, posing a serious problem associated with the stabilization of the quality of the batteries. Further, a lot of time is required for the evaluation in charge and discharge tests, and an anode should be combined with an electrolyte to constitute a cell.
Thus, the development of a method for evaluating a material for a cathode material, which, after the production of a cathode material powder, can rapidly predict the properties of a battery by a powder evaluation method sensitive to the distribution and valency of Mn ion and the like, has been earnestly desired for the development of cathode materials and the stabilization of the quality of the battery.